Diabetes mellitus is a mammalian condition in which the amount of glucose in the blood plasma is abnormally high. Elevated glucose levels in some instances can lead to higher than normal amounts of a particular hemoglobin. This condition can be life-threatening and high glucose levels in the blood plasma (hyperglycemia) can lead to a number of chronic diabetes syndromes, for example, atherosclerosis, microangiopathy, kidney disorders or failure, cardiac disease, diabetic retinopathy and other ocular disorders, including blindness.
Diabetes mellitus is known to affect at least 10 million Americans, and millions more can unknowingly have the disease. There are two forms of the disease. In the form of this disease known as Type II, non-insulin dependent diabetes mellitus (NIDDM) or adult-onset (as opposed to juvenile diabetes or Type I), the pancreas often continues to secrete normal amounts of insulin. However, this insulin is ineffective in preventing the symptoms of diabetes which include cardiovascular risk factors such as hyperglycemia, impaired carbohydrate (particularly glucose) metabolism, glycosuria, decreased insulin sensitivity, centralized obesity hypertriglyceridemia, low HDL levels, elevated blood pressure and various cardiovascular effects attending these risk factors. Many of these cardiovascular risk factors are known to precede the onset of diabetes by as much as a decade. These symptoms, if left untreated, often lead to severe complications, including premature atherosclerosis, retinopathy, nephropathy, and neuropathy. Insulin resistance is believed to be a precursor to overt NIDDM and strategies directed toward ameliorating insulin resistance can provide unique benefits to patients with NIDDM.
Current drugs used for managing Type II diabetes and its precursor syndromes, such as insulin resistance, fall within five classes of compounds: the biguanides, thiazolidinediones, the sulfonylureas, benzoic acid derivatives and alpha-glucosidase inhibitors. The biguanides, e.g., metformin, are believed to prevent excessive hepatic gluconeogenesis. The thiazolidinediones are believed to act by increasing the rate of peripheral glucose disposal. The sulfonylureas, e.g., tolbutamide and glyburide, the benzoic acid derivatives, e.g. repaglinide, and the alpha-glucosidase inhibitors, e.g. acarbose, lower plasma glucose primarily by stimulating insulin secretion.
Among biguanides useful as diabetic therapeutic agents, metformin has proven particularly successful. Metformin is an anti-diabetic agent that acts by reducing glucose production by the liver and by decreasing intestinal absorption of glucose. It is also believed to improve the insulin sensitivity of tissues elsewhere in the body (increases peripheral glucose uptake and utilization). Metformin improves glucose tolerance in impaired glucose tolerant (IGT) subjects and NIDDM subjects, lowering both basal and postprandial plasma glucose.
Unlike sulfonylureas, metformin does not produce hypoglycemia in either diabetic or non-diabetic subjects. With metformin therapy, insulin secretion remains unchanged while fasting insulin levels and day-long plasma insulin response can decrease. Metformin also has a favorable effect on serum lipids, which are often abnormal in NIDDM patients. In clinical studies, particularly when baseline levels of lipids were abnormally elevated, metformin lowered mean fasting serum triglycerides, total cholesterol, and LDL cholesterol levels and had no adverse effects on other lipid levels.
There is a need in the art for new formulations of metformin that are therapeutically effective in treating diabetes. The invention is directed to this, as well as other, important ends.